Rate of Reactions Flashcards
What is the definition of the rate of reaction?
The rate of reaction is the speed at which reactants are converted into products in a chemical reaction per unit time.
What is a catalyst?
A catalyst is a substance that increases the rate of a reaction buy lowering the activation energy, without being consumed in the process.
What is the collision theory?
Collision theory states that for a reaction to occur, reactant particles must collide with sufficient energy and proper orientation.
What is the significance of activation energy in a chemical reaction?
Activation energy is the minimum energy required for reactants to collide and react.
What is the difference between a homogeneous and a heterogeneous catalyst?
A homogeneous catalyst is in the same phase as the reactants, while a heterogeneous catalyst is in a different phase.
What happens to the rate of reaction at the beginning?
The rate is fastest at the beginning of a reaction as each reactant is at its highest concentration.
What occurs to the rate of reaction as it proceeds?
The rate slows down as the reaction proceeds because the concentration of reactants decreases.
When does the rate of reaction become zero?
The rate is zero when the reaction stops, which occurs when one reactant has been used up.
How are rates of reaction measured?
Rates are measured by measuring the concentration of a reactant or product over a certain period of time.
What factors can affect the rate of a reaction?
- Surface area of a solid
- Concentration of a solution
- Temperature of the reaction
- A catalyst
- Pressure of gaseous reactions
- Light (in some light-sensitive reactions)
What is collision theory?
For a chemical reaction to occur, the reacting molecules have to collide with the correct force and direction.
What is activation energy?
The minimum energy required for the reaction to occur.
What are energy profiles used for?
They compare the enthalpy of reactants with products for both exothermic and endothermic reactions.
What happens in an exothermic reaction?
The reactants lose energy and heat is given out to the surroundings.
What does a positive ∆H indicate?
The products have more energy than the reactants and energy is absorbed from the surroundings.
How does concentration affect the rate of a reaction?
The rate of a reaction increases if the concentration increases due to more molecules in the same volume.
How does pressure affect reactions involving gases?
Increasing the pressure increases the concentration per unit volume, leading to more collisions.
What is the effect of particle size on reaction rate?
Smaller particles react more quickly than large particles due to increased surface area.
How does temperature influence reaction rates?
The rate of a reaction increases with an increase in temperature due to higher kinetic energy of molecules.
What is the role of a catalyst in a reaction?
It provides an alternative route of lower activation energy, allowing more particles to react.
What are the two types of catalysts?
- Homogeneous
- Heterogeneous
Why are heterogeneous catalysts commonly used in industry?
They are easy to separate from the products.
What are some benefits of using enzymes as catalysts?
- They don’t harm fabrics and food
- They are biodegradable
- Lower temperatures and pressures can be used
- Pure products are usually formed
What methods can be used to measure rates of reaction?
- Change in volume of a gas
- Change in pressure
- Change in mass
- Change in color
What is the iodine-clock reaction?
It involves the oxidation of iodide ions by hydrogen peroxide, indicated by a blue color with starch solution.
What is the purpose of the gas collection method?
To measure the rate of any chemical reaction that produces a gas.
What is the cross on paper method used for?
To calculate how quickly the reaction between sodium thiosulfate and hydrochloric acid takes place.
What is the relationship between concentration and rate in a reaction?
Rate is proportional to 1/time.
